Control apparatus



y 1947. R. H. JOHNSON CONTROL APPARATUS Filed Feb. 4, 1942 3 Sheets-Sheet l INVENTGR ROBERT JOHNSON 1 wrr vi f May 6, 1947. R. H. JOHNSON CONTROL APPARATUS Filed Feb. 4, 1942 5 Shams-Sheet 2 INVENTOR Roacnr H. JoHNsoN ATTORNEY y 6, 1947- R. H. JOHNSON 2,420,043

CONTROL APPARATUS Filed Feb. 4, 1942 3 Sheets-Sheet 3 a #f n INVENTOR Roeilrr H. Jormson BY A Patented May 6, 1947 Robert H. Johnson, Weston, W. Va. Application February 4, 1942, Serial No. 429,483

13 Claims.

The present invention relates to a control apparatus and method for automatically regulating a condition, such as, for example, regulating the temperature in a heated building.

One of the objects of the present invention is to provide a control apparatus and method for effecting control of a condition, which apparatus effects such control in accordance with movement ber in response to changes in the condition, but without the members necessarily contacting one another.

Another object of the invention is to provide a control apparatus and method for efiecting changes in a condition according to the movements of a member responsive to changes in the condition, the control apparatus being effective to cause the changes at intervals and according to the position of the movable member at these intervals.

Still another object of the invention is to provide a control apparatus and method for a heat exchange system for a building, for example, in which the temperature of the building is affected crease or decrease in temperature of the burner, thereby forestalling over heating and under cooland the changes in the temperature of the air in the building and minimizing fluctuation in the air temperature in the building.

It is also an object of the invention to provide a control apparatus and method similar to that described in the preceding paragraph in which the device responsive to the temperature of the )uilding modifies the efiect of the device responierature, the rate at which the temperature of he fuel burner changes is proportionally hanged, respectively. 7

Still another object of the invention is to conrol the rate of movement of a valve that is eflecve to increase or decrease the rate of combuson in a heating system, for examplaso that the rte of movement of the valve will be proportional changes in temperature of a medium being mtrolled from a predetermined temperature.

flue pipe 24.

the damper 22 is closed the damper 23 is fully preferred forms of. embodiments of thepresent invention are clearly shown.

In the drawings: I

Fig. 1 is a fragmentary view of a building heated by a furnace, the furnace being controlled by my improved controlapparatus and method;

10 Fig.2 is a diagrammatic showing of the control apparatus; and, V Fig. 3 is a diagrammatic showing of another form of control. apparatus.

15 various conditions, it is particularly suitable for Heated air is directed from the furnace to the room through ducts, one of which is shown at 26.

The dampers 22 and 23 are interconnected by a chain or cable 28 that rides on pulleys 29 and The length of the chain is such that when opened, and vice versa. The dampers are actuated by an electric motor 32 that is connected to the chain 28 by a crank 33. When the motor 35 rotates the crank 33 counterclockwise, as viewed in Fig. 1, through 180, damper 22 is opened and. damper 23 is closed. The motor 32 is a reversible type, and stops, not shown, are provided for limiting the movement of the crank 33 to'rotation 40 through 180.

The motor 32 is controlled by switching mechanism indicated generally at 34. The switching mechanism is in turn controlled by a temperature responsive device 35 that is located in the room 20 and also by a device 36 which, prefer exchange relation with the air in the bonnet of the furnace. The device 36 is responsive to the rate of change in the temperature of the air in a pivot for the lever and the bi-metal strip 40 extends from the hub. The position of the free end of the bi-metal 40 can be adjusted by rotating a cam 43, as the lever H is continually urged against the periphery of the cam by a spring 44. An electric heating element is carried on the end of the bi-metal strip and is insulated from the strip. The heater element is a low voltage type and is energized by a step-down transformer 41. The primary winding 48 of the transformer is connected to the usual 110 volt household power lines 49 and 50 by wires and 52. The secondary winding'53 of the transformer is connected to the heating element by wires 54 and 55. The heating element 46 is arranged to be moved by deflection of the bi-metal 40 intermediate juncof a thermocouple indicated generally at 60, so that these junctions are heated above atmospheric temperatures preferably by radiant heat. The thermocouple 80 comprises a U shaped constantan wire 8i having the ends thereof joined with copper wires 62 and 83' at 58 and 59. The wire BI is preferably shielded from the heat of the heater 4'6 except at the junctions 58 and 59. The circuit for the thermocouple 80 includes a galvanometer 61 and a thermopile 88, which latter comprises the device 38. The wire 82 is connected to the thermopile 88 at a junction 10 and the wire 83 is connected with a The lever 4| is adjusted by the cam so that when the temperature of the bi-metal 40 is 72 F., for example, the heater tween the junctions 58 and 59 and each junction is subjected to the same intensity of radiant heat, and therefore, the temperatures of these junctions will-be substantially'the same. It is to be understood, however that the lever 4i could be that the heater element would be midway between the junctions of the thermocouple at other temperaturesthan 72 F. As the temperature of the bimetal decreases, the heater element 48 is moved toward the junction 59 for increasing heat at that junction while causing a decrease in the intensity of the heat at the junction 58. This increases and decreases the temperatures of the junctions 59 and 58, respectively. When the temperature of the bimetal is raised above 72 F., the heater element is moved nearer to the junction 58 and that junction becomes the junction 59. Thus, on a decrease in temperature of the bimetal below 72 F.-an electric potential will be established tending to cause a flow of current through the thermocouple circuit from wire 6| to wire 63, and on an increase in temperature above 72 F., the flow of current or potential will be established in the opposite direction. When the heater element is exactly intermediate the junctions, both junctions' are heated equally and no current'will be generated.

The junction 10 tions 58 and 59 of thermopile 68 is connected with a constantan wire 1|. The opposite end of the wire H is joined with one end of a copper wire 12 at junction 13 and the opposite end of the wire 12 is connected to a constantan wire Hat junction 15. The opposite end of the wire 14 is connected to a copper wire 18 at junction 11. The junctions 18 and are each in close heat exchange relation with a mass of heat absorbing material 19, such as copper, so that the temperatures of the wires at these junctions will lag with respect to changes in ambient temperature. The junctions 13 and 11 are each in close heat exchange relation with masses smaller the intensity of the radiantterminal 88 of the galvanometer.

element 48 is mid-way bemature 83 and thermopile 88. will be at than those of junctions 10 and 15 or they may be exposed directly to changes in temperature so that when the thermopile is subjected to changes in temperature, there will be a differential in temperature between the junctions 10 and 15 and 11, respectively. The thermopile 88 is subjected to the air in the bonnet of the furnace.

The wire 16 is connected to a terminal 18 of the galvanometer 81, and the coil of the galvanometer is connected in series with the thermocouples 60 and 88 through the terminals 88 and 18.

It will be apparent that when the temperature of the air in the bonnet increases, the temperatures of the junctions 13 and 11 of the thermopile will increase more rapidly than the temperatures of the junctions 18 and 15 and, therefore, an electric current will be established in wire 18 tending to flow toward the coil 80. When the temperature of the air in the bonnet decreases, the thermopile 68 will establish an electric current tending to flow in the opposite direction since the junctions 13 and 11 will be cooler than junctions 10 and 15. When the temperature of the air in the bonnet of the furnace is constant or substantially constant, the junctions oi! the the same temperatures, and therefore; no potential-will be established by it. Thus, the thermopile establishes an electric potential proportional to 'the rate of change in temperature, and the direction of flower current is-dependent on whether the temperature is increasing or decreasing.

It will be noted that the thermocouple 88 and thermopile 88 establish currents of the same polarity, or augment one another, whenever the temperature of the bimetal 40 is above or below 72F and the air in the furnace bonnet is increasing or decreasing, respectively, and that potentials are established counter to one another whenever the temperature of the bimetal 40 is above'or below 72 F., while the temperature or the air in the furnace bonnet is decreasing or increasing, respectively.

The galvanometer 51, a top plan view of which is shown diagrammatically in Fig. 2, is conminal 88 of the galvanometer the potential at the terminal 18, be deflected in a counter-clockwise direction, for example, and when the potential at 18 is greater than at 86, the coil will be deflected in a clockwise direction. When the potentials are exactly the same or zero, the coil will be in the position shown in Fig. 2. It is apparent that the galvanometer is responsive to the algebraic sum of the potentials established by the thermopile and thermocouple.

An armature 8i, which is mounted on a vertical pivot 82, is oscillated by movement of the coil 80, and this armature carries an iron ara contact bar 84.

Two suitable electromagnets, shown diagrammatically at and 86, are arranged on opposite sides ofthe armature 83 and are equally distant from the armature when the coil 80 is in the position shown in Fig. 2. The magnets 85 and 88 include coils '81 and 88, respectively, and these coils are connected in series. The coil 88 is connected to the line 50 by a wire 89 and to the coil 85 by wire 98. Coil 81 is connected to the line 49 by a. circuit including a wire 9|, time switch 92 and wire 93.

The time switch 92 includes a contact bar 84 two switches, I26 and I21.

that is adapted to bridge two contacts connected with wires 9| and 93, respectively. The contact bar 94 is arranged to be closed on the contacts periodically by a cam 96. The cam 96 is mounted on .a shaft 91 that is drivemby-an electric timing motor 98 and is provided with a' lift 99.

A cam follower I rides on the periphery of the cam and is attached to the contact bar 94 for causing the switch 92 to be closed by the lift 99 of the cam. Preferably, the motor 98 is adapted to rotate the cam at the'rate of two revolutions per minute and the lift 99 is formed so that the switch 92 is closed fo approximately five seconds during each revolution. The windmg I 0| of the motor 98 is connected with the line wires 49 and 50 by wires I02, I03 and I04. Thus, the magnets 85 and 86 are energized'every thirty seconds and they remain energized for approximately five seconds. If the armature 8| is in the position shown in Fig. 2, the pull of the magnets on the armature 83 are neutralized and the armature 8| will remain stationary. However, if the armature 8| is deflected toward one or the other of the magnets, due to current passing through the coil 80 in one direction or the other, the armature 83 will be attracted to the nearer magnet when themagnets are energized, and the contact ba 84 will bridge contacts I06 or contacts I01 according to the direction of flow of current in coil 80. Preferably,-the coil 80 is incapable of moving armature 8| sufficiently to cause the contact 84 to closecontacts I06 and I01 independently of the action of the magnets.

The closure of contacts I06 causes the energization of a coil II 0 of a magnetic relay III through the following circuit: line 49, wires' I I2, II3, coil IIO, wire II4, contacts I06 and 84, wires II5, and I04 to line 50. When the contact 84 closes contacts I01, a coil I20 of a magnetic relay I2I is caused to be energized by a circuit established from line 49 through wires II 2, I22, coil I04 to line 50. g r

The magnetic relay III,when energized, closes The closure of switch I26 establishes a circuit through'a furnace control device such as the motor 32 as follows: from line 49 through wires I29, I30, motor winding I3I, Wire I32, switch I26, wires I33 and I34 to line 50. The winding I 3| in the embodiment shown, causes the motor 32 to rotate in the direction to open the damper 22 and close the damper 23, for example, for causing an increase in the draft through the furnace and consequently the rate of combustion. The closure of switch I21 establishes a holding circuit 'for therelay III as follows: line 49, wires H2, H3, coil 0, wires II4, I36, switch I21, wires I31, I38, switch I40, wires I39 and I04 to line 50. The-switch I40 is normally closed and it is arranged to be opened by a cam I4I that is mounted on the shaft 91. A cam follower I42 rides on the periphery of the cam and engages the movable contact of the switch I40. The follower I42 is actuated by a lift I 43 on the periphery of the cam and causes the switch to be opened for approximately one second and then reclosed during the time that the switch 92 is closed by the cam 96. Preferably, the cam I4I the switch I40 will reclose just prior to reopening of switch 92. This will allow at least several seconds for the armature 8| to be attracted to one or the other of the magnets 85 and 86 before the holding circuit is broken.

The magnetic relay I2I, when energized, closes I20, wire I23, contacts I01 and 84, wires I25, and

1 A holding circuit for I29,. I41, motor winding I48, wire I49, switch I45,

wires I50 and I34 to line 50. Energization of the'winding I48 inthepresent embodiment causes the motor 32 to rotate in the direction to and open the damper 23.

close the damper 22' the relay I 2| is also established from line 49 through wires II 2. I22, coil I20, wires I23, I5I, switch I46, Wires I52, I38, switch'I40, wires I39 and I04 to line 50.

The galvanometer 61 and tor 98 and the relays III and in a suitable housing and comprise the switching mechanism 34. This mechanism can be located in the furnace-room, for example.

Preferably, the motor 32 operates-the dampers 22 and 23 relatively slowly, 90 seconds, for example, to move the dampers from their closed positions 9 and vice versa. This will I of combustion since the motor 32 will be energized is positioned on the shaft 91 so that for periods of approximately 30 seconds, and if at the end of these periods conditions at the devices 35 and' 36 havechanged, the motor will be deenergized or reversed by the mechanism 34. By.renergizing-the motor for fthese periods; the action of the motor is positive. ijeiZfitwilfnot alternate its direction during the time that the control phases are about to be'reveised bythe devices 35 or 36. A.ls0, by providingf a. relativey sl w p ng damper control for a coal burning furnace, better combustion of the'coal will be obtained.

Whenthe control system is in operation, the heater element 46 is energized and the motor 98 is operating for periodically closing switch 92 and opening switch I40. Assuming that the damper 22 is closed, the damper 23opened'and the room temperatureis at 72 F. ;.the;parts of I will be in the positions shown in.Fig..;2. When switch 92 is closed for the control apparatus energizing magnets and 8G,.thearmat will remain in its neutral positionlan f control motor 32 will remain deener'gized Ifthe temperature in the roomgshou ld fall below '72, the increased heating at the junction 59 of the thermocouple 60 causes a potential 'to be established at the terminal 66 of the galvanometer 61. This causes thefarmature to be deflected toward magnet 86, and when the magnets and 86 are energized by the closure of the time switch 92, the armature 83 is drawn to the magnet 86 which causes the contact 84 to close contacts I06. This energizes magnetic relay I II which in turn causes energization of the winding 3| of the motor 32. The motor 32 operates to cause the damper 22 to move toward the fully open position and causes the damper 23 to move toward closing position for increasing the rate of combustion. After the switch 92 is'closed for five seconds, it is reopened, but the relay III is maintained energized through it holding circuit thatincludes the switch I 40. As the temperature of the air in the bonnet 36 increases, due to the in creased rate of combustion in the furnace. the temperatures of the junctions 13 and 11 of the thermopile 68 increase over the temperaturesof the junctions 10 and 15, thereby establishing a potential at the terminal 18 of the galvanometer opposing the potential established by the thermocouple 60. If the rate of increase in the change of temperature in the air of the bonnet of the furnace is a certain value, it will cause the poten- 6 When switch I45 is closed;

requiring a period of to fully open positions] produce closer control --perature of the air in to close damper 22 be maintained without causing an in the bonnet of tial established by the thermopile 88 to neutralize or overcome the efiect of the potential at the terminal 66 and cause the coil 88 to return the armature 83 to or move beyond, the neutral position. If the armature 8| is returned to its neutral position, when the switch 82 isclosed, the armature will remain in its neutral position and the switch I40 will be opened and 'deenergize the magnetic relay III. This causes the switch I26 to open and deenergize themotor 32. If the temthe bonnet of the furnace continues to increase, due to the open draft damper 22, the potential established at. the terminal 18 by the thermopile 68 will cause the coil 88 to deflect the armature 8! in the direction of the magnet 85 and when the switch 82 is closed, thearmature 83 will be drawn to the magnet 85 and cause closing of the contacts I81 for energizing the relay I2 I. This relay closes the circuit for causing the motor 32 to rotate in the direction and to open damper 23 to thereby decrease the rate of combustion. When the'fiow of current through the coil 80 is zero, due to the algebraic sum of the potentials established by the thermopile and thermocouple being equal to zero or substantially zero,-the switch I40 will open and deenergize the relay i2 l since the armature 83 will be in itsneutral position when switch 82 is closed. v

Although the room temperature may remain below 72 R, if the rate of increase in temperature of the air in the bonnet is great enough, the thermopile 68 will establish suflicient potential to cause the coil 80 of the galvanometer to be defiected for causing the armature 8| to come under the influence of the-magnet 85 and cause the mechanism 34 to reverse the motor 32-for decreasing the rate of combustion. It is to be noted that the further the temperature in the room decreases from 72, the thermocouple 80 will establish a higher potential in the galvanometer coil, and before the a counter potentialfor causing a decrease in the rate of combustion in the furnace, the rate of temperature increase inthe bonnet will have to be correspondingly greater. Thus, the temperature responsive device 35 affects the effective responsiveness of the device 38 so that under extremely cold conditions the rate of increase in temperature of the furnace is increased. In this manner, the proper rate of combustion will always over-ride" in the temperature of the room. 1 e

If, the room temperature should increase above 72 F., the heater element 46will be moved toward the junction 58 of the creasing the temperature of that junction and reducing the temperature of junction 59. This establishes a flow of electric current in the circuit of the thermocouple in the direction for causing the mechanism 34 to cause the motor 32 to move the draft damper 22toward closed position and move damper 23 toward open position for reducing the rate of combustion.

If, while the room temprature is above 72, the rate of reduction in the temperature of the air value, the thermopile 68 will establisha current counter to the current established by the thermocouple 60 and cause the galvanometer to move to its ,neutral' position for checking changes in the positions of the dampers, or the potential generated by the thermopile might affect the control mechanism to cause reopening of the draft damper. Thus,the sensitivity ofthe device 36 therrnopile 88 can establish I thermocouple 80 for inthe furnace exceeds a certainto changes in rate of decrease in temperature of the air inside the bonnet of the furnace is afiected in proportionto the temperature of the room above 72. For example, asthe temperature of the junctions l3 and I1 of the'thermopile falls below the temperature of the junctions l and 15, an electric potential is established tending/to coil in the direction cause flow of current through the galvanometer for causing themotor 32 to toward the open position. As the room increases above '72, 60 will establish a potential move the damper 22 the temperature of the thermocouple counteracting that produced by the thermopile always be maintained in the and in proportion to the rise in temperature above 72. Therefore, as the room temperature increases above 72, the rate at which the temperature in the furnace bonnet decreases must increase before the thermopile will be effective to cause opening of the damper motor to increase combustion. v

It is apparent that by controlling the combustion in the furnace according to the rate of change in the temperature thereof, the furnace will produce in actual practice, substantially only that amount of heat that is necessary to maintain the desired temperature in the room being heated and the furnace will never become colder Therefore,

temperature and daily-eliminated and a uniform temperature can room being heated.

The sensitivity of the control apparatus to the rate of change in temperature of the air in the bonnet of the furnace can be increased by adding more thermocouples to the thermopile.

It is apparent that either one of the devices '35 and 36 can take over the control of the damper motor 32 or they can control operation ofithe motor jointly.

I do not consider it essential that the device 38 be employed in my controlsystem, since the device 35 could control the switching mechanism independently of the 'device 36. However,

' closer and more satisfactory control oflthe furnacecan be had by incorporating in the control system.

Referring to Fig. 3, I have shown another embodiment of the invention in which the rate of movement of the dampers 22 and 23 is regulated in accordance with the demands for changes in the rate of combustion. In this embodiment, the dampers 22 and23 of the furnace 2| are actuated by an electrically driven motor 232, The motor 232, in the present embodiment, is an induction type motor and it operates at a relatively high speed, such as 3400B. RM, and it requires more than five seconds to attain its maximum speed. Suitable speed reducing mechanism, not shown. is interposed between the motor and the crank 38 for actuating the dampers so that the dampers will be operated at a slow speed, which speed will be more fully defined hereinafter. Preferably, the motor is designed so that the momentum created by energization of the motor for several the I device 38 seconds causes the; motor to coast at least onehalf minute after the motor is deenergized. This motor is also reversible.

The winding circuits for the motor 232 are controlled by two relays 3H and 32!, which relays operate switches 326 and 345, respectively. These switches are closed when the relays are energized and opened when the relays are deenergized.

The relays 3H and MI are controlled by a galvanometer 261, which galvanometer is similar the. lag between the furnace room temperature is substanto the galvanometer 61 and which is controlled.

235 and 236. The devices 235'and 236 by devices to devices 35 and 36 described hereinare similar before, and are responsive to theair temperaflowing therethrough, and two opposed electromagnets deflected 285 and 286 are arranged to move the armature positively in the direction of deflection when the magnets are energized. When the armature is attracted bythe magnet 285 or magnet 286, the contact 284 is arranged to close the contacts 301 or 306, respectively, It is to be understood that the galvanometer 261is operated by'the devices 235 and 236 in the'same mannerthat the galvanometer 81 is operated by thedevices 35 and 36.

When contacts 306 are closed by the contact 284, a circuit is established through the relay 3| I as follows: power line 49, wire 3|2, coil 3! of the relay,'wire 3l4, contacts 306 and 284, wires 3i5 and 304, to power line 50.

Energization of relay'3ll closes switch 326, for establishing a circuit for the motor 232 as follows: line 49, wires 329, and 330, winding 3 3i of the motor232, wire 332, switch 326, and wires 333 and .334 to line 50. In'the present embodiment energization of winding 33l causes the armature of motor 232 to rotate in a direction for opening damper 22 and closing damper 23 of the furnace 20. 7

When contacts 301 are closed by the contact 284, a circuit is established through the relay 32| as follows: line 49, wires 3I2 and 322, magnetic coil 320 of the relay, wire 323, contacts 301 and 284, wires 325 and 304 to line 50. Energization of relay 32l closes the switch 345 for establishing the following circuit for motor 232: line 49, wires 329 and 341, winding 348 of the motor, wire 349, switch 345 and wires 350 and 334 to line 50. Energization of winding 348 causes the armature of the motor 232 to rotate in a direction to cause closing of damper 22 and opening of damper 23;

The magnets 285 and 286 are energized by the following circuit: line 49, wire 293, time switch 292, wire 29!, coil 281, wire 290, coil 288 and Wire 289 to line 50. The switch 292 is closed by a cam 296 that is mounted on a shaft 291 driven by an electric motor 298. The cam 296 is provided witha lift 299,'and a bridging contact bar 294 is carried by a cam follower 300, which follower rides on the motor 298 is arranged to operate continuously and to rotate the cam 296 two revolutions per minute. The lift 299 is formed for causing -the switch 292 to be closed for approximately five seconds during each revolution of the cam. The motor 298 is energized by the following circuit: line 49, wire 302, winding 30l and wires 303 and 304 to line 50.

If, for example, the potentials established by either one or the other, or both of the devices 235 or 236 cause the galvanometer 261 to deflect the armature 28! toward themagnet 286 when periphery of the cam.' The The momentum of the motor will cause it to con tinue to move the draftdamper 22 toward open position and. damper 23;toward closed position, although the motor is deenergized. When the cam 296 again closes the switch 292, if the armature 28| is still deflected toward the magnet 286 the relay 3 will be reenergized by'the magnet 286 drawing the armature towardit and the 'motor 232 will be energized again for a period of five seconds or less, depending on the rapidity with which the armature 28! is drawn toward the magnet, during which time'it will gain speed and accelerate the rate of movement of dampers 22 and 23. Preferably, the speed reducing mecha 'nism mentioned hereinbefore; is such that the motor 232 moves the dampers 22 and23 from closed to fully open positions when the motor 'is energized for four 5-second periods during four revolutions of the cam 296; It will be understood,

of course, that during actual operation, the motor 232 may be reversed before the position of the dampers are fully' reversed, and that under cir I cumstances' described hereinafter, the motor 232 may operate at lowerspeeds, therefore requiring more time to move the dampers from'one extreme position to the other.

When the armature 28l' of the galvanometer 261 is deflected but slightly'from its neutral pois unaffected by either it may require several to be moved to close 301, after the magnets sition, in which position it of the magnets 285 or 286, seconds for the armature either the contacts 306 or 285 and'286 are energized. If, for example, it

would require two seconds for closing the contacts 306, the motor 232 would be energized for approximately three seconds. Consequently, atthe end of the three seconds the motor would be moving at a relatively low overcome its starting inertia, and the dampers would be moved at, a relatively slow rate. This would tend to cause an increase-in the combus tion in the furnace at a relatively slow rate, but since the galvanometer 261 indicated a very slight need for increased combustion, the combustion would be regulated accordingly. The same condition would prevail for moving the dampers in the opposite direction, i. e., for reducing the rate of combustion. It is apparent, that when the armature 28! of the galvanometer is deflected substantially from its neutral position, when the magnets 285 and 286 are energized, thearmature will be deflected substantially immediately to the nearest magnet and cause the motor 232 to be energized for substantially five seconds.

Since the speed of the motor is dependent upon the duration of the periods that it is energized,

' combustion.

the switch 292 is closed, the magnet 286 deflects It is to be understood that anysuitable device may be used to cause movement of the dampers at a rate proportional to the duration of the periods at which the relay circuits are energized.

Thus, by my invention, a valve, in this case the damper 22, for controlling the rate of combustion can be moved at speeds proportional to thedemand for combustion, thereby tending'to maintain the furnace at the proper temperature at all times. This provides a modulating control that can be used for operating fuel valves for gas or oil burners so that a very close temperature can be maintained.

By my invention, a control apparatus is prospeed since it must mostatic devices.

. scope of the claims which follow.

'I claim: a V

1. In a heat exchange system, a heat exchanger and a medium aflected by means for causing a change in the temperature of the exchanger; and means responsive to rate of change in temperature of theheat exchanger for controlling the rate of said change of temperature, said first mentioned means also varying the effective responsiveness of theisecond mentioned means to a rate of-changein temperature of the heat exchanger in proportion to the change in temperature of the medium from a predetermined temperature, said first mentioned means including a' device responsive to the medium for varying the effectiveness of the first mentioned means. 7

2. In a heat exchange system, a heat exchanger for aiIecting the temperature of'a medium; means for establishing an electric potential proportional to the deviation of the temperature to which said means is subjected from a predetermined temperature; means for establishing an electric potential counter to the first mentioned potential and the temperature of proportional to the rate of change of temperature to which the last mentioned means is subjected, one of said means including a device subjected to the temperature of the medium for varying the eifectiveness of the said means and the other of said means being subjected to a temperature corresponding to changes in the temperature of the exchanger; and means responsive to the algebraic'sum of said potentials for controlling the temperature of the heat exchanger.

3 In a heat exchange system, a heat exchanger for affecting the temperature 01' a medium; electroresponsive means for changing the temperature of the heat exchanger; gizing the first mentioned means including, an element responsive medium for establishin a current potential for afiecting the first mentioned .means and an element responsive to the rate oi change of the temperature of the heat exchanger for establishing a current potential opposing potential.

4. In a control system, a control member mov- V able in response to changes in a condition to be controlled, said member including an armature; means forming a plurality of magnetic fields, each of said fields exerting equal magnetic forces on said armature when the armature is in a predeterminedposition; timing means for rendering the magnetic fields. effective and ineffective substantially simultaneously; and means controlled by said member for afiecting said condition when said member is moved from said predetermined position in response to a change in sald condition and attracted by either of said fields.

5. In a control system, a controlmember movable in response to changes in a condition to be controlled; means providing a source of energy operable for moving said member to a predetermined control position when the member is moved to a certain position in response to a. change in andmeans for enerto the temperature of the l the first mentioned 'said condition;

12 means providing a second source as energy operable for moving said member toa second predetermined position when the member is moved to a differentpredetermined position in rsponse to a different change in said condition; timing means for rendering said first and second means efiective and ineffective substantially simultaneously; and means controlled by said member when moved b either of said flrstand ill the heat exchanger;

second means for affecting said condition. 6; In a heat exchange system, a heat exchanger and a medium affected thereby; means responsive to an electric potential for controlling the heat exchange between the exchanger and the medium; means for varying the electric potential including two thermocouple elements, one oijsaid thermocouple elements being more sensitive to temperature changes of the heat exchanger than the other, said second means including a third thermocouple elementior modifying the potential; and means responsive to the temperature of the medium for-varying the eflectiveness of the third mentioned'thermocouple. l

. '7. In a heat exchange system, a heat exchanger and a medium afiected thereby; means responsive to an electric potential for controlling the heat exchange between the exchanger and the medium; means for varying the electric potential including two thermocouple elements, one oi. said thermocouple, elements being more sensi; tive to temperature changes of the heat exchanger than the other, said second means including two thermocouple elements for modifying the potential; and means responsive to the temperature of the medium for increasing and decreasing the potential effect of one of the last two mentioned thermocouple elements and' simultaneously decreasing and increasing the potential effect of the other of the two last mentioned thermocouple elements.

8. A control systemincluding in combination, a device to be controlled; a thermocouple including two junctions; heat exchange means thermally associated with the thermocouple junctions; means movable in one direction for causing the heat exchange means to establish one of said junctions asa cold junction and the other as a warm junction and movable in the opposite direction for causing said heat exchange means to change the cold junction to a warm junction and the warm junction to a cold junction; means responsive to the flow of current in said thermocouple in one direction for effecting the operation of said controlled device in a certain manner and responsive to the flow of current in said thermocouple in the opposite direction for effecting the operation of said controlled device in another manner and means responsive to the effects produced by the controlled device for effecting said movements 01! themovable means.

9. A control system comprising in combination, a variable capacity device for affecting the condition of a medium; an electrical circuit including an electrically operated controller for con- 'trolling the output of said device, an electrical generator capable oi! generating current in either direction and of variable potential in either direction of flow, the direction of flow and the capacity of current generated thereby being dependent upon the rate of change of output of said device, a second electrical generator having a variable capacity, said electrically operated controller being controlled by the algebraic sum of the current generated by said generators; and means responsive to the condition of the medium affected by said device for controlling the cur rent output of the second mentioned generator;

10. A control system comprising in combination, a variable capacity device for afiecting the condition of a medium; an electrical circuit including an electrically operated controller for controlling the output of the device, a variable capacity electrical generator, the capacity of said generator being variable in response to the rate of change of output of said device, a second electrical generator capable of generating current in either direction and of variable potential in either direction of flow, said electrically operated controller being controlled by the algebraic sum of the current generated by said generators; and means responsive to the condition of the medium afiected by said device for controlling the direction of current flow and current output of the second mentioned generator,

11. A control system comprising in combination, a variable capacity device for affecting the condition of a medium; an electrical circuit ineluding an electrically operated controller for controlling the output of said device, an electrical generator capable of generating current in either direction and of variable potential in either direction of flow, the direction of flow and the capacity of current generated thereby being dependent upon the rate of change of output of said device, a second electrical generator capable of generatin current in either direction and of variable potential in either direction of flow, said electrically operated controller being controlled by the algebraic sum of the current generated by said generators; and means responsive to the condition of the medium afiected, by said device for controlling the direction of current flow and current output of the second mentioned generator.

12. A control system including in combination, a device to be controlled; generating means operable for establishing a. first electric potential and operable for establishing a second electric potential having its polarity opposite that of the first mentioned potential, said generating means including two elements subjected to controlling medium, the potential established being dependent upon the difference of intensity of said medium on said elements; means responsive to the potential established for controlling the operation of said device; andmeans responsive to the operation of the controlled device for ina device to be controlled;

while substantially the intensity of the ment.

ROBERT H. JOHNSON.

REFERENCES CITED The following 30 file of this patent:

references are of record. in the UNITED STATES PATENTS Number Reid June 12, 1928 

